Use of geologic maps as indispensable tools in the modern search for oil or ore deposits and as the first essential step in unraveling the story of the earth we live on is well known. Less well known, perhaps, is the fact that topographic and geologic maps contain many of the basic data needed for planning any engineering construction job, big or little. Any structure built by man must fit into the topographic and geologic environment shown on such maps. Moreover, most if not all construction jobs must be based on knowledge of the soils and waters, which also depend entirely on this same environment. The topographic map shows the shape of the land—the hills and valleys, the streams and swamps, the man-made features, such as roads, railroads, and towns. The geologic map shows the kinds and shapes of the rock bodies that form the land surface and lie beneath it. These are the facts around which the engineer must build.